1. Field of the Invention
The invention relates to a four-wheel industrial truck with a swing axle.
2. Technical Background
When narrow curves are cornered the lateral moment of tilt which results from the centrifugal force may become larger for such vehicles than is the righting moment, and the vehicle topples over. It has become known from EP 0 483 493 to provide an alerting device for the industrial truck that includes a monitoring device for the condition of load. The load moment acting on the vehicle and the actual constellation of the vehicle are sensed. Unstable conditions are determined by means of this data and are signaled to the driver.
It is known from EP 0 796 749 to block the swing axle when unstability is impending. Such blockage is dependent on the angular velocity rate sensed or calculated for the vehicle.
It has become known from DE 101 18 442 A1 to provide a sensor, preferably on the vehicle frame or bodywork, which senses the distance of the vehicle frame from the swing axle. When this distance reaches a predetermined lower or predetermined upper value a relevant correction or alerting signal is produced. When a sensor is arranged on either side of the swing axle the threshold of response is formed by a lower distance value each. Additionally, the document has it made known to provide another sensor on the vehicle frame, preferably adjacent to the front axles, that measures the distance of the frame from the underlying ground.
When the ambient conditions are satisfactory a distance measurement of the type described can be readily performed by means of non-contacting optical, inductive or acoustic sensors. An industrial truck, when in operation, is subjected to harsh conditions. Therefore, sensors of the type described are exposed to hazards and there is a danger of a message not being made in case of impending unstability.
It has become known from WO 79/00330 to detect the inclination of a pole relative to the underlying ground by the use of a load-carrying means, e.g. with the aid of a potentiometer. The driver is signaled the angle measured and the driver of the industrial truck will be able to correct the position of the load-carrying means by tilting the pole accordingly. DE 199 19 655 A1 further has made it known for an industrial truck to associate at least one wheel with a load sensor. A safety device has a comparing facility which provides a signal to an alerting signal transmitter when one or more of the loads measured on a wheel fall below a predetermined value. This is intended to recognize an unstability or an approach to an unstability of the vehicle on time in order to counteract it. The sensor signals can act upon one or more functions of an industrial truck, namely on the height of load, steering angle, speed of the vehicle, pole inclination, shift of the load-carrying means in the direction of the longitudinal axis or also transversely thereto, height adjustment of one or more shock absorbers or the like. Further, a stabilizing device may be provided and may be activated accordingly.